The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Samyang 10mm f2.8 and the Canon 20mm f2.8 USM for their suitability to various photography scenarios:
Size and Weight Comparison
The size of a lens is a crucial factor to consider when comparing two lenses. Samyang 10mm f2.8 is the longer of the two lenses at 77mm. The Canon 20mm f2.8 USM with a length of 71mm, is 6mm shorter. Besides being longer, the Samyang 10mm f2.8 also has a larger diameter of 86mm compared to the Canon 20mm f2.8 USM's 78mm diameter.
The weight of a lens is equally significant as its external dimensions, particularly if you intend to handhold your camera and lens combination for extended periods. Canon 20mm f2.8 USM weighs 405g, 30% (175g) lighter than the Samyang 10mm f2.8's weight of 580g.
Below you can find the dimension and weight table of the Wideangle Prime Lenses in Canon EF Mount for size comparison purposes.
Ultra-Wideangle Lenses in Canon EF Mount for Size Comparison
Lens Mounts
Both the Samyang 10mm f2.8 and the Canon 20mm f2.8 USM has the same Canon EF lens mount. Some of the latest released cameras that are compatible with the Canon EF lenses are Canon T8i, Canon 90D and Canon SL3.
Samyang 10mm f2.8 is also available in the Canon EF-M , Fujifilm X, Nikon F (DX), Four Thirds and Micro Four Thirds mounts.
Focal Range
Samyang 10mm f2.8 is a prime lens with fixed focal lenght of 10mm which has an effective (full-frame 35mm equivalent) focal range of
16mm when used on a APS-C / DX format camera.
On the other hand, the Canon 20mm f2.8 USM is a prime lens with fixed focal lenght of 20mm. When it is mounted on an APS-C sensor camera with 1.6x crop, it provides a 35mm (FF) equivalent of 32mm.
